In order to achieve a reproducible on-line pretreatment of slurry samples in flow-injection analysis the dispersion behaviour of these samples has to be examined. This paper reports the effects of flow rate and some configurations of reaction manifolds. The reaction manifolds were a straight tube and two helically coiled tubes with different aspect ratios and spatial orientation. The slurry samples consisted of spheres of different densities suspended in a Triton X-100/water solution, the particle diameters (up to 75 ¿m) were relatively large compared to the internal diameter of the tubing (0.75 mm). For the straight tube theoretical calculations were found to give a reasonable impression of the experimental flow behaviour of the spheres. Statistical moments were used to characterize the slurry peaks. For tightly coiled tubes it was found that the retention time of a slurry sample depends on the particle density. The spatial orientation of the coils mainly affects the retention of high density particles.